This invention relates to automotive air conditioning systems in general, and specifically to an electrically controlled compressor that has control communication through the compressor housing without a direct wire connection.
A recent trend toward electrically driven, rather than engine belt driven compressors, promises to provide better and more efficient control, as well as eliminating clutches and seals around the drive shafts. Since a mechanical drive shaft with its rubbing seal no longer pierces the compressor housing, such compressors are sometimes referred to as being hermetically, completely sealed. This is somewhat of a misnomer, since a power carrying wire, instead of a shaft, must pierce the compressor shell to carry current to the motor. While not a moving part, the power wire must still be sealed at its interface with the housing. It is desirable to drive such compressors with a brushless electric motor, often referred to as a brushless DC motor, though it is actually an AC type motor. Since an automotive vehicle has only a DC primary electric source, an inverter is necessary to effectively convert the DC current to AC current, to act, in essence, as the equivalent of a conventional mechanical brush and commutator assembly to switch the current. There are also potential advantages to physically incorporating the inverter and its associated electronics inside the compressor shell, providing a compact package, short interconnections, and even the ability to cool the power electronics with the inlet refrigerant. Other sensors may be incorporated within the compressor shell, also. In that case, another wire or even wire bundle would, conventionally, have to pierce the compressor shell to provide two way communication between the vehicle controller and the compressor control electronics. This would require yet another pressure tight seal at the interface.
The invention provides a compressor having a shell that incorporates control electronics internally, but which does not require that a deparate data carrying line physically pierce the compressor shell, with its associated seal. Instead, an assembly consisting of a first optical transmission device inside the compressor housing acts across a suitably transparent, small window through the compressor shell, transmitting and or receiving data to or from a corresponding second optical device outside the compressor shell. The optical window is a solid piece which can effectively be made integral to the compressor shell itself, and is thus very tightly sealed.